Excess-demand meter



A. W. BURKE.

Excess DEMAND METER. APPLICATiGN, FILED DEC. 16. 1916.

. A Innen/fed July 1, 19m.

'UNITED sTATEs PATENT ernten ALFRED W. BURKE. OF WYNNEWOOD,PENNSYLVANIA.

Specification of Letters Patent.

' EXCESS-DEMAND METER.

Application led December 16, 1918. Serial No. 267,013.

energy:- overa predetermined quantity and that is substantiallyunaffected Ain accuracy by variations in 'voltage or power factor of theload in the supply circuit.

This result is accomplished by the use ot' a specially designedtransformer, called a compensaton the magnetic circuit ot which isnormally operated at a flux density above its magnetic saturation point.The secondary current from the compensator therefore substantiallyconstant regardless ot' changes in the primary current above a positivetorque on the rotatable member ot the meter, this positive torquebalancing the negative torquewhen the predetermined amount ot energy isconsumed and upon the use of energy in excess o't the prede,-

-termined demand overbalancing the negaponentis so .proportioned that atnormal tive torque andcausing the meter to record the excess.-

My invention also provides means by-A which the current vt'or producing`this positive torque is made up o't' two components, one substantiallyin phase with the voltage on the linel circuit, and the othersubstantially in phase with the load, so that the registrationl of themeterr is accurate not only for variation-s in voltage, but also forvariations inthe power factor of the supply circuit.

In the draWings,-

Figure 1 is a diagrammatic representation of' the preferred method ofcarrying out my invention Fig. 2 is a diagrammatic representation of amodified form;

Fig. 3 is a diagrammatic representation of another modification.

`lteferring to F ig. 1 ot the drawings, the alternating current mains,2, 3, are shown, as connected to the load L through an excess-dcmamlmeter, comprising a high resistance potential coil 12, and two current.coils 11 and 2O mounted upon a U-sl1aped magnetic core. The windings onthe coils t 11 and 20 are so connected that the instanl taneousmagnetizing elf'ccts are opposite. The windings on the coils 11 and 12coperate to produce a magnetic field tendingl to rotate the armature 1Gbackward, while those on coils :'20 and 12 tendto rotate the .armatureforward. The current for the coil 11 is furnished from the secondary 9of a transformer 8 having a saturated core. The primary T of thistransformer receives cur rent from the secondary of a step-downtransformer 5, whose primary l is connected 'across the supply mains. 13and 13( are adjustable resistances. For clearness sake the transformers5 and 8 have been shown as separate. They may of course be combined intoone.

The current flowing through coil 42() is made up of two components, (1)current flowing throllgh circuit 'formed by wires 22, 23, the load L,and wire 24; and (2) current flowing from the secondary 19 ot step-downtransformer 1T whose )rimar 18 is conv 7 and the second with thevoltage.Each com- `,corresponding to the eustoiiies'rlemand, so

that the combined effect of thetwo componente at demand load 1s toproduce a normal forward torque eorrcspomling to twice 4the customci"sdemand.

`The current. supplied to winding 11 is such that the torque produced bywindings 11 and 12 is negative, fi. c. tends to rotate the meterarmature baclnvard and is equal to the combined normal forward torque ofPatented July 1., 191.9.

g l l1,308,656

both the forward components above referred to, z'. e. this backwardtorque is twice' the torque produced by either forward compo` nent'.

The current delivered to winding 11 is substantially constant becausethe core o f transformer 8 is' so designed as to be niagneticallysaturated at any voltage liable to occur in use.V The armature shaft maybe prevented from backward movement by a ratchet, 14 and pawl 15, or anyother suitable intermittent clutch device.

lVith the meter thus arranged it will be apparent that at normal voltageand no load, the meter will tend to rotate backward lunder a torquecorresponding to the normal demand. As the load comes on, this backwardtorque will be diminishedrbecause of current flowing through coil'20 andthe load, until the demand current has been reached, when the twotorques willbe balanced. Upon use of current in excess of the demand,the forward torque will prevail and such excess energy will be recordedby the meter. If, however, the voltage increases, the current to winding20 from transformer 17 will increase in direct proportion as also thatin high resistance potential winding 12, with the result that the`effect of the load current on winding 20 will cause a torque balance tobe reached before the normal demand load current is reached, thewatt-meter, however,-

beginning to record the excess energy 1n watts as soon as'the normaldemand in watts is exceeded. The'i'ncrease in current from secondary 19to coil 2 0, due to the voltage increase, just compensates in effect onthe demand for the effect of thev increase in strength of potentialwinding 12, the Aresult being that the demand is not affected by thechange in voltage.

Similarly, if theyolta-ge on the line decreases,-the current componentdue to transformer 17 will .decrease and the negative torque will not bebalanced until ,the load current component has a current valueabove .thenormal current-demand at normal volt-A age. But, in this case also, thewatt-meter will begin to record as soon as there is used any power,expressed in watts, above thedemand rate. l 1

It is evidentuthat'. by the arrangement described the meter operates torecord excess power only when the demand as expressed in watts isexceeded. The torques acting in the meter disk maybe analyzed asfollows: The negative torque is a function of the ,constant I current,in the coil 11 and of the ciiri'cntin the coil 12-varymg with thevoltage. The

forward torque is a function of the currents flowing in coll-:i` 20 and12. the current in the coil 20 varying with the load and with thelvoltage. The currentiii the voltage coil 12 and that. current componentin the coil 20 which is a function of the load current cothe transformer19 varies with the voltage and offsets. the variationof the negativetorque due to fluctuations of the current in coil 12. Normally i'. c. atnormal voltage the efect of the current 'diie to transformer 19 justbalances the effect of one half of the current flowing through coil 11.As the line voltage varies the current component diie to transformer 19varies and the increase or decrease of' current just compensates for theincrease or decrease of current in coil 12. In this manner-the positivetorque due to the cooperation of coil 12 and the component in coil 20which is a function of the load current is modified to compensateaccurately for the variations of the negative torque with the resultthat the'positive or forward torque is strictly proportional to the rateof power used in excess of the demand expressedV in watts. r

It will further be apparent that the feurrent flowing through lwinding20 is'the vector sum of the current induced by the shunt transformer 17,which current is a function of theline voltage, and the current intlt'load circuit itself. lf the line current lags behindtliefline voltage,c. if the power factor ijsless than-1, the torque produced by thecoperation of coils l20 and 12 decreases t0 that extent. The watt-metertherefore registers true watts and not' volt-amperes. As long as a-'constant current from the transformer 8. with the saturated corepasses through a separate coil, such as 11', the meter will registerthe` excess power correctly, re-` gardless ofthe power factor of theload.

Only one element of a polyphase meter need be thus equipped to give therequired" negative torque, and the other element can be oftlhe standardform and will furnish the positive torque I Droportional. to the currentand voltage.

`While I have shown diagraminatically a particular form of inductionnictcr, it will be understood that the invention is applicable to othertypes of electric energy meters.

A modified form of arrangement for producing a similar result is shownin Fig 2, in which'a different, method of supplying current to the metercurrent coil shown. In this ligure,l 17 is a transformer comj'irising aprimary shunt coil4 18', a, priii'iary load coil 19, and a secondarycoil 20.v The shunt coil 18 connected across the lines 2, 3, andthecurrent flowing through it is therefore pro- )ortional to and varieswith the line'voltage'.

he coil 19 is connected in serieswiththe load L and the current flowingthrough it is the load current. -The instantaneous values of the currentinduced in the secndary -20 alle tliiisa function of the vectorsumsoftln'- load current and line voltage.

The secondary 20 is connected to the current coil QOin the watt-meter10, this currentcoil 2.0 being, asbefore-described, so connected to thesecondary 20 that it produces witlpthelpotential coil 1'2 a positivetorque, .fe. turns the meteil disk forwardly. The transformer secondary9 and current coil 11 are so designed thatl the current coil 11`produces iifconjunction with thevoltage coil 12 at normal voltage anegative torque proportional to twice the demand.

Coils 1S, 19, 29 and 20 are so designed that the` current induced insecondary .29

' by the shunt coil 1S', at normal line voltage, produces a positivetorque, through the coA 'and potential coil 12 will correspond to twicethe. demand,` while the positive torque produced by the current coil Q0and potential coil 12 willem-respond exactly tothe predetermineddemand/1'. c. one half of the negative torque. f

's the load comes on and the current passing through the load coil 19increases to the normal load current, the positive torque,

' tive torque produced by the currents which are. induced by the shuntcoil V18 and the load.A coil 19"l and flow' through current coilQO. f l

All energy consumed in excess ot the tlc-- mand, be -it due to increaseot' the load current or line voltage or both, causes an increaseot1 theypositive torque in excess of the negative torque and this excess ot'positive. torque is substantially proportional to the excess consumptionof energy.-

If for instance,l the line voltage rises, the shunt coil 18 suppliesmore current andthe positive torquedue to coils l2 and E20' increases inproportion. A less amount of line current required to balance thenegative torque and as soon as this value is exceeded, the meter beginsto register.

Conversely, it' the voltage drops,`the currentA flowing through theshunt coil "18 is less, and the positive torque due to this currentdecreases in proportion. Not until the line current has risen above thenormal .would the negative torque be balanced, and

\ the circuit o't wim ln Fig, 3 is illus-tufted still anothermodification in which thesaturatcd core transformer is connected inseries with the load. The watt-meter has the uslal `potential coil- 99and current coil 9S y(Itwo opptgrd current 70 coils may bc uscd assllown in l" l). The transformer 1T has La seclfindary winding- 96` andthree primary windings 93; 9-l and 95. The winding 94 is in series withthe load L, a relay 97, and the primary 91 ot a 75 saturated coretransformer. The secondary 92 ot' this transformer is connected throughan adjustable resistance R to winding 93. 'lhe winding is connectedthrough adjustable resistance K across the line. and its circuit isarranged to be interrupted by a'switch controlled by relay 97. At normalvoltage, and normal demand, the windings 94 and 95 have the same numberot ampere turns` while the winding 93 has twice that number 85 of ampereturns, the core ol the transformer being so constructed as to besaturated at or below the normal load current; The winding 93 is woundt`o produce a current ot' such direction as to produce a negativetorque. in the meter, while coils 94 and 95 are wound to produce apositive torque. The operation ot this form of the device will beyreadily understood from the foregoing description.

At normal load and voltage," no current 95 will be produced in thcsecondary 96 as the magnetic ett'ects 'of winding 93 will be balanced bythose of windings 94 and 95. Upon increase of voltage, the etlect o't'winding 95 will be increased and the meter will 100 begin to register ata rate of current flow less than normal. It the voltage decreases` ythelessened amount otl positive torque trom winding 95 will permit a largerthan normal current quantity ot' current to flow through 105 winding 94lbet'ore the fixed wattage demand `point is reached. The true excesswat'ts used will be recorded on account ot' these variations. 'lhe relayS?" is so adjusted as to open ing 95 before. the load cur- 110 rentfalls below a point where the magnetic etl'ect of winding 93 would besmaller than the combined effect ot windings 94 and 95.

I claim: 1. In an instrument. for measuring electrical energy consumedin excess ot' a predetermined fixed rate, the combination ol a movableelement. means for producing thereon a positive torque which isafunction ot' the rate ol energy consumption. and means operative toproduce thereon a substantially constant negative torque, the lattermeans comprisine' meanstor producing'a negative. torque. which isvariable as a function ol the. line voltage, and means tor producing aposi-tive torque. variable as a function of the line voltage, said twolatter torqnes being so related to each other as to produce inconjunction a constant negative torque.

tric energy, a voltage' coil, a current coil and means for passing asubstantially constant current therethrough, another current coil, meansfor passing a current therethrough which is a function of the linevoltage, means for passing a current therethrough which is a function ofthe load current, said current coils being so arranged that they producein' conjunction with the voltage coil" torques in opposite directionsand that the resul-tant torque equals zero when the rate qfenergyconsumption represents a fixed demand', and that the positive torqueswill prevail :When

the energy consumed is'in excess of the de mand.

3. Inan instrument for measuring elec- -tric energy, a voltage coil, acurrent coil, a

` lsaid current-coil, another current coil, transyconstant currenttransformer connected to former means for passing a current therethroughwhich is a function of the line voltage, means for passing a currenttherethrough which is a function of the load current, said current coilsbeingvso arranged lthat they produce torques in opposite direc- 'tionsand that the resultant torque equals zero when the rate of energyconsumption represents a ixed demand, and that the positive toi-queswill prevail when the energy consumed is inexcess of. the demand.

4. In an instrument for measuring electric energy in excess of a certain4demand i comprising a movable element, means for prodiiiugajsubstantially constant negative torqu'evproportional to twice thedemand,

means .responsive to the line voltage for producing a positive torquewhich is substantially proportional to the demand When `the line voltageis normal and means responsive to the load current for producing apositive torque substantially proportional .to

the load current.

5. In an instrument for measuring electric energy in excess of a certaindemand vcomprising ainovahle element, a voltage coil I:and two currentcoils, n'i'eans for passing a constant current through one of saidcurrent coils and means for passing a current through the second currentcoil which is a "50 function of the vector sum of the load current andthe line voltage, the said means and current coils being so constructedand 'arranged that the torques produced thereby oppose each othe` andthat the resultant torque equals .zero when the rate oi energy`consumption represents the demand.

`(3. In an instrument for measuring electric energy in excess of 'acertain demand i comprising a .movable element, a voltage coil and twocurrent coils, a constant current transformer having its secondaryyconnected to one of the said current coils, another transformer having aprimary connected across the line, and its secondary 'connected to theother current coil which is in series with the load, Ithe transformersand current coils being so constructed and arranged that the turquesproduced by the current coils in conjunction with the voltage coiloppose each other and that the resultant torque equals zeroWhen'the'line voltage and line current represent the demand, and thatthe positive tor., es will prevail when the energy consumediis 'inexcess of the demand. l

7. In an instrument for measuring electric energy in excess of a certaindemand comprising a movable element, a voltage coil and two -currentcoils, means for passing a constant. current through one of .saideurrent coils to produce in conjunction with the voltage coil asubstantially constant ne tive torque, proportional to' the nornialnmandin Watthours, means for passing' through thesecond current coil a'current having two components, one component being a function` of theload current and the" saturated coretransformer, for passing a constantvcurrent through one of said current coils, means' for supplying currentto the other current coil comprising (1i) a direct connection in serieswith the load. and (2) a transformer.having its'primary connectedacross. the line, and its secondary lconnectedto said other currentcoil,.the transformers and current coilsbeing soconstructed and arrangedthat the torque produced by the current coils in conjunction with thevoltage coilfoppose'eacli other, that the resultant torque on themovable member equals zero when the line voltage andload currentrepresent `a tixed demaud,'and that the positive toi-ques will prevailwhen the energy consumed is in excessl of the fixed demand. v

In testini'ony whereof, I aiiix my signature.

" ALFRED lV. BURKE.

Ill(i

